Underground tracking system in the works for MBTA Green Line

Massachusetts Bay Transportation Authority (MBTA) announced yesterday that it plans to install an underground tracking system for Green Line trolleys that will enable riders to use their smartphones to obtain real-time arrival times.

The system will use tracking devices known as Automatic Vehicle Identifiers (AVIs) to provide data on the trolleys' whereabouts. MBTA had installed GPS devices on all Green Line trolleys in October 2014, but since that technology doesn't work underground, the agency needed to retrofit the tunnels with AVI technology.

The hardware will also use the data to display arrival times on message boards, according to MBTA spokesman Joe Pesaturo.

MBTA aims to complete the installation in the next four months.

The agency received a $13.4 million grant from Massachusetts Department of Transportation to fund the entire Green Line tracking project.